1. Field of the Invention
The invention concerns a device for projecting a color image onto a screen, the device enabling color image recording and a color image reproduction with greater fidelity than possible with existing techniques. In an alternative embodiment, the device and the therewith employed process provides for full color stereoscopic image reproduction.
2. Description of the Related Art
In existing devices and processes for image recording in full color, the color information is detected by the separate recording of the respective spectral regions which correspond to the primary colors red, green and blue. In the subsequent image reproduction, the primary color partial pictures are combined into a full color image. A device of this type is known for example from WO WO98/49837.
Fundamentally, both in photochemical processes as well as in electronic processes, photoelectric transformers are involved in reproducing visual contents in color.
The length and the breadth of the mentioned spectral regions is largely dictated by the spectral sensitivity of the color receptors in the human eye. Typical values for both image recording as well as image reproduction lie in the wavelengths of
spectral region blue430–480 nmspectral region green500–550 nmspectral region red600–650 nm
Each of these spectral regions can, via its color coordinates, be assigned a point on the standard color chart ((x, y)-chromaticity diagram) according to DIN 6164 (Mutze et al., ABC of Optics, published by Dausien, Hanau, 1972). The totality of all of these principle colors defined in this manner—the primary valences (reference stimulus) (see U.S. Pat. No. 4,409,614, incorporated herein by reference)—form a triangle in the standard color chart, as shown in FIG. 1 (continuous line). By an additive color mixing of the basic colors, each color can be represented within this triangle. Colors outside of this triangle cannot be represented. In particular, spectrally pure colors with their characteristic high color saturation—these lying on the outlying peripheral curve, the spectral color chart curve—are not reproducible.
One possibility for enlarging the representable color space is comprised in the selection of primary valences with narrower spectral ranges for image reproduction. In the extreme case the primary valences (primary colors) are finally spectrally pure and lie on the spectral color curve, as shown in FIG. 1 (dashed line). However the price for the thus achieved enlargement of the color space, for example in projection systems which use broad band emitting temperature radiators (bodies that deliver radiant heat, whose frequency (color) depends on the temperature, commonly used as wide-band strong sources of light) as projection lamps, is a substantial loss in image intensity. This becomes more distinct with the narrowing of the bandwidth of the base colors, since out of the entire emission spectrum only correspondingly small emission ranges are utilized.
If on the other hand one employs spectrally pure light sources, such as for example lasers, then this disadvantage does not occur. However, such systems are very complex and expensive. Besides this, the enlarging of the color space does not necessarily result in increased color reproduction fidelity. Rather, calculations must be made on the enlarged color reproduction side as well as on the recording side. Otherwise, there could result false colors which must be corrected using suitable color transformers. The later however results again in a reduction in the size of the color space.